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						<h1 id="firstHeading" class="firstHeading" lang="en"><span dir="auto">Camera response curve</span></h1>
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								<div id="siteSub">From PanoTools.org Wiki</div>
								
												
				<div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><p>The <b>camera response curve</b> is
a curve showing the relation between amount of incoming light and image pixel values of a digital camera.
</p><p>This curve is sometimes also called <b>Opto-Electrical Transfer Function</b>. 
</p><p>Although optical sensors work quite linear (a certain amount of photons coming in causes a proportional amount of electrons in the sensor cell), the resulting pixel values are not proportional to the amount of incoming light. This might have several reasons: 
</p>
<ul>
<li> The analog-digital converter might not work linearly. 
</li>
<li> A <a href="Gamma.html" title="Gamma">Gamma</a> correction is applied.
</li>
<li> A correction is applied to make the image more visually appealing
</li>
<li> A white balance is applied to compensate for different light temperature
</li>
</ul>
<p>While the first reason applies to all kinds of images, the other ones apply to non-RAW (<a href="JPEG.html" title="JPEG">JPEG</a>, <a href="TIFF.html" title="TIFF">TIFF</a>) images only. <a href="RAW.html" title="RAW">RAW</a> images should contain linear sensor data.
</p><p>The <b>camera response curve</b> is an issue mainly in <a href="HDR.html" title="HDR">HDR</a> generation where it is necessary to have linear (proportional to light) input data. Non-linear data (= a badly estimated camera response curve) will result in banding in contrast gradients (f.e. around bright lights).
</p>



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